1. Field of the Invention
The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus which carries out image recording by ejecting and depositing ink onto a recording medium from an inkjet head while rotationally conveying the recording medium which is wrapped about and held on the outer circumferential surface of a drum.
2. Description of the Related Art
In general, an inkjet recording apparatus performs recording by ejecting and depositing droplets of ink onto a recording medium from nozzles arranged on an inkjet head, and the apparatus is able to record images of high resolution and high quality, with little noise during the recording operation and low running costs, and therefore is widely used in a variety of fields.
An inkjet recording apparatus is known which has a cylindrical recording drum and an inkjet head disposed in a position opposing the outer circumferential surface of the recording drum, an image being recorded by ejecting and depositing ink from the inkjet head onto a recording medium while rotationally conveying the recording medium which is wrapped about and held on the outer circumferential surface of the printing drum. In a recording apparatus of this kind, there is a problem in that the recording medium is liable to float up from the outer circumferential surface of the recording drum and deterioration of image quality is liable to occur. Therefore, one important technical issue is to hold and secure the recording medium on the outer circumferential surface of the drum in a tightly adhering state.
Japanese Patent Application Publication No. 11-240217 discloses a drum which is composed in such a manner that, in order to be able to carry out image recording in a stable fashion onto recording media of different lengths, a medium supporting surface formed in a circumferential direction between a leading end gripping device capable of gripping the leading end of a recording medium and a trailing end gripping device capable of gripping the trailing end of same can be extended and contracted in accordance with the length of the recording medium. However, in this drum, although the medium supporting surface can be extended and contracted in accordance with the length of the recording medium, since the trailing end gripping device projects to the outside of the drum, then it is not possible to dispose a guide member in close proximity in a position opposing the outer circumferential surface of the drum, and consequently it is not possible to make the recording medium adhere tightly to the drum. For this reason, if a thick and strong paper is used as the recording medium, then there is a problem in that the recording medium is secured in a state where the recording medium is floating up from the drum.
Japanese Patent Application Publication No. 2002-292956 discloses a drum which has suction apertures formed in the whole of the outer circumferential surface (paper sheet supporting surface) thereof, where a recording medium is held and secured by applying a suction pressure (negative pressure) through the suction apertures. However, in this drum, no consideration whatsoever is given to stably holding recording media of different lengths, and hence there is a problem in that the number of different paper sizes that can be recorded on is small. Furthermore, by simply raising the suction pressure applied to the suction apertures formed on the whole of the outer circumferential surface of the drum, suction leaks occur in the suction apertures located in portions which are not covered by the recording medium, and hence there is a problem in that the trailing end portion of the recording medium cannot be sucked adequately. Consequently, it is difficult to hold and secure thick strong paper in a state of tight adherence to the outer circumferential surface of the drum, without the paper floating up from the drum.